Electrical Fundamentals - Borg Warner Delco Remy 28MT Diagnostic Procedures Manual

1-9. BATTERIES. Batteries are perishable devices that wear out
at some point in time. With use, they deteriorate and eventually
become incapable of performing their important job. In addition,
new batteries may become discharged for various reasons.
Neither worn out nor discharged batteries can supply the power
necessary for cranking. Thus, the battery check becomes the
starting point for diagnosing electrical system problems.
1-10. SUBCIRCUITS. Because of vibration, corrosion, temperature
changes or damage, the performance of wiring, connections and
secondary components as well as the function of the starter and
alternator can deteriorate. This, in turn, can cause malfunctions
within the starting and charging systems. For the purpose of
testing, wiring and components are divided into four circuits that
must be tested. These are:
1. Cranking Circuit. This consists of the large cables that carry
the high starter current. Excessive loss here causes slow cranking
speeds, especially in cold weather. Inability to start from slow
cranking can lead to starter damage if the starter is cranked over
30 seconds. Deeply discharged or worn-out batteries also can
cause the same problem.
2. Solenoid Circuit. This consists of the wiring from the battery,
through a push button or magnetic switch, to the S terminal of
the starter solenoid, and back to the battery. Excessive loss here
can cause the solenoid to shift in and out (chatter), resulting in a
no-start condition. This can cause a damaged contact disc and
terminals of the starter solenoid. Deeply discharged batteries also
can cause this problem.
3. Magnetic Switch Circuit or IMS (when the magnetic switch is
used). This consists of the wiring from the battery, through a key
switch and/or start button, to the coil of the magnetic switch, and
back to the battery. Excessive loss here can cause a "no start"
complaint.
4. Charging Circuit. This consists of the wiring between the
alternator and the battery and back to the alternator. Excessive
loss here can cause the batteries to not charge properly. As noted
above, discharged batteries will cause other problems.
1-11. SEQUENCE OF PROCEDURES.
procedures be followed in the exact sequence specified. Batteries,
wiring and connections should be checked and corrected to
the specifications given. If cranking problems still occur, then
connecting cables should be checked before replacing the starter
with a known good unit. Similarly, in the charging circuit, the
batteries, wiring and connections should be thoroughly checked
and corrected to the specifications given. Only then should the
alternator be checked and replaced if necessary.

1-12. ELECTRICAL FUNDAMENTALS

1-13. TERMS AND DEFINITIONS.
and definitions used in this manual:
It is important that these
The following are electrical terms
1. Voltage. Voltage is the electrical pressure or force that causes
current or electrons to flow through a conductor. The voltage
also can be described as the difference in electrical pressure
between two points in a circuit. This electrical force or pressure is
measured in volts.
2. Current. Electrical current is the flow or movement of electrons
in a conductor. This movement can be compared to the flow of
water through a pipe. Without pressure (voltage), the current
will not flow. Electrical flow is measured in amperes, most often
abbreviated as amps.
CURRENT
3. Resistance. Resistance is the opposition to current flow. For
a given electrical pressure (voltage), resistance decreases current
flow. This can be detected by voltage loss or drops in the electrical
circuit. Electrical resistance is measured in ohms.
4. Magnetic Field. When electrical current flows through a
conductor, a magnetic field is produced around the conductor.
By measuring the strength of this magnetic field, it is possible
to determine the amount of the current flow or amperage. This
principle is the basis for the function of the clamp-on or induction
type ammeter.
1-14. MEASURING VOLTAGE WITH THE VOLTMETER.
voltmeter is used to measure electrical pressure or voltage. The
unit of measure is the volt. Voltmeters are always connected
across (in parallel with) a part of the electrical circuit (See Figures
1-6 and 1-7). The voltmeter measures the difference in electrical
potential or pressure between the points where the voltmeter is
attached.
1-15. VOLTMETER SELECTION.
described in this manual are DC instruments with a range as
follows:
1. Low scale: 0-3 volts
2. 12-volt vehicles: 0-16 volts
3. 24-volt vehicles: 0-32 volts
MAGNETIC FIELD
DP-1005
The
Voltmeters for the purposes
Page 2